MX2014007611A

MX2014007611A - Method for forming a thermoplastic composition that contains a renewable biopolymer.

Info

Publication number: MX2014007611A
Application number: MX2014007611A
Authority: MX
Inventors: James H Wang; Gregory J Wideman
Original assignee: Kimberly Clark Co
Priority date: 2011-12-20
Filing date: 2012-12-18
Publication date: 2014-09-15
Also published as: US20130154151A1; EP2794214A4; WO2013093781A1; AU2012356190A1; EP2794214A1; CN103987504A; BR112014015070A2

Abstract

A method for forming a thermoplastic composition that contains a combination of a renewable biopolymer with a polyolefin is provided. The biopolymer and polyolefin are supplied to the extruder at a feed section. The plasticizer is directly injected into the extruder in the form of a liquid so that it forms a thermoplastic biopolymer in situ within the extruder and then a homogeneous blend. The in situ addition of the plasticizer is facilitated by the use of a compatibilizer that has a polar component with an affinity for the biopolymer and a non-polar component with an affinity for the polyolefin. When the polymers are initially added to the extruder, the compatibilizer can help facilitate the ability of the biopolymer to be melt processed for a short time until it can be rendered thermoplastic through mixture with the plasticizer. Further, upon mixing with the plasticizer, the compatibilizer can also help ensure that the resulting composition remains generally homogeneous and does not separate into constituent phases.

Description

METHOD FOR FORMING A THERMOPLASTIC COMPOSITION CONTAINING A RENEWABLE BIOPOLIME BACKGROUND OF THE INVENTION Natural polymers are produced in nature by the absorption of carbon dioxide, a greenhouse gas responsible for global warming. Materials containing natural biopolymers will have a reduced environmental footprint in terms of overall energy savings, reduction of greenhouse gas emissions, etc. throughout the life cycle of the products, which includes raw material productions, manufacture, distribution, use, elimination at the end of life, and so on. Particularly, there is a greater commercial need to develop biodegradable thin films based on biomaterials for use in the field of absorbent articles, such as baby and child care products, feminine hygiene products, and adult incontinence products, etc. . For example, these films can be used in the lower canvases of the absorbent articles. None of the current biodegradable materials based on commercially available biomaterials alone satisfies the application needs of such products. Polylactic acid, for example, is generally too rigid for flexible film applications Ref. 249534 It is silent and tends to have a performance in terms of use, such as causing noisy creaking in adult women's products. Aliphatic-aromatic copolyester films, such as Ecoflex® films are synthetic polymer films made from petroleum and do not contain any natural or biomaterial-based polymer components necessary for the intended application and their costs are also too high for such applications planned. Pure copolyester films also exhibit poor conversion processing capacity for the manufacture of cast films. The resulting films are too sticky and can not be collected by rolling on a roller. In addition, co-polyester cast films tend to block easily which makes them very difficult, if not impossible, to separate into individual layers after production. It has also been tried with the thermoplastic starch, but it can not be manufactured in thin films due to its limited processing capacity. The pure starch thermoplastic films are also very fragile and too rigid to be useful in soft flexible film applications.

In view of these difficulties and deficiencies of currently available materials, there is an unmet need for thin films for personal care product applications. It is highly desirable to invent relatively inexpensive polymer blends formulations that can be used to create a soft and malleable thermoplastic cast film containing a significant amount of biodegradable components of natural origin.

SUMMARY OF THE INVENTION According to one embodiment, a method for forming a thermoplastic composition is described. The method comprises supplying a renewable biopolymer, a polyolefin, and a compatibilizer to a feed section of an extruder, wherein the compatibilizer has a polar component and a non-polar component. A liquid plasticizer is injected directly into the extruder so that the plasticizer is mixed with the biopolymer, the polyolefin, and the compatibilizer to form a mixture. The mixture is melt processed into the extruder to form the thermoplastic composition.

According to another embodiment of the present invention, a method for forming a film is described. The method comprises supplying a renewable biopolymer, a polyolefin, and a compatibilizer to a feed section of an extruder, wherein the compatibilizer has a polar component and a non-polar component. A liquid plasticizer is injected directly into the extruder so that the plasticizer is mixed with the biopolymer, the polyolefin, and the compatibilizer to form a mixture. The mixture processed by melting inside the extruder to form a thermoplastic composition. The composition is extruded through a die and onto a surface to form a film, wherein the film has a thickness of about 50 microns or less.

Other features and aspects of the present invention are discussed in more detail below.

BRIEF DESCRIPTION OF THE FIGURES A complete and workable description of the present invention, including the best mode thereof, addressed to a person skilled in the art, is more particularly set forth in the remainder of the description, which refers to the accompanying figures in which: Fig. 1 is a partially cut away side view of an extruder that can be used in an embodiment of the present invention; Fig. 2 is a schematic illustration of one embodiment of a system for cooling the thermoplastic composition that can be employed in the present invention; Y Fig. 3 is a schematic illustration of one embodiment of a system for forming a film according to the present invention.

The repeated use of reference characters in the present description and in the figures is intended to represent the same or analogous features or elements of the invention.

DETAILED DESCRIPTION OF THE INVENTION Definitions As used herein, the term "biodegradable" generally refers to a material that is degraded by the action of naturally occurring microorganisms, such as bacteria, fungi and algae; the environmental heat; humidity; or other environmental factors. The degree of degradation can be determined in accordance with Test Method 5338.92 of the ASTM.

As used herein, the term "renewable" generally refers to a material that can be produced or derived from a natural source that is periodically replenished (eg, annually or perennially) through the actions of ecosystem plants terrestrial, aquatic or oceanic (eg, agricultural crops, edible and inedible grasses, forest products, seaweed or algae), microorganisms (eg, bacteria, fungi or yeast), and so on.

Reference is now made in detail to various embodiments of the invention, of which one or more examples are set forth below. Each example is provided by way of explanation of the invention and not of limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made to the present invention without departing from the spirit and scope of the invention.

For example, features illustrated or described as part of one embodiment may be used in another embodiment to produce an additional embodiment. Thus, it is intended that the present invention cover such modifications and variations that are within the scope of the appended claims and their equivalents.

Generally speaking, the present invention is directed to a method for forming a thermoplastic composition containing a combination of a renewable biopolymer (eg, starch polymer) with a polyolefin that improves the biopolymer's processability and also helps improve certain mechanical properties of the resulting film. Contrary to conventional techniques for incorporating a biopolymer into a thermoplastic composition, the method of the present invention does not involve precomposing the biopolymer with a plasticizer. Instead, the biopolymer and the polyolefin are fed to the extruder in a feed section. The plasticizer is injected directly into the extruder in the form of a liquid so that it forms a thermoplastic biopolymer in situ within the extruder and then a homogeneous mixture. In this way, the pre-encapsulation or precomposition steps of the plasticizer and the biopolymer in a thermoplastic biopolymer are not required which are costly and time consuming. Despite facing a series of challenges, the present inventors have found that the In situ addition of the plasticizer is facilitated by a compatibilizer having a polar component with an affinity for the biopolymer and a non-polar component with an affinity for the polyolefin. Such a compatibilizer can have benefits for the composition both in the short and long term. That is, when the polymers are initially added to the extruder, the compatibilizer can help facilitate the ability of the biopolymer to be melt processed for a short time until it can be made thermoplastic through the mixture with the plasticizer. In addition, when mixed with the plasticizer, the compatibilizer can also help to ensure that the resulting composition remains generally homogeneous and does not separate into its constituent phases. This results in a finely dispersed polymer system that exhibits the combined attributes of good polymer processing capacity, biodegradability, and mechanical strength.

Various embodiments of the present invention will now be described in more detail.

I. Components A. Biopolymer The biopolymer that is employed in the thermoplastic composition of the present invention can include, for example, starches, as well as other carbohydrate polymers, such as cellulose or cellulose derivatives (e.g., cellulose ethers and esters), hemicellulose, etc. , - lignin derivatives; protein materials (eg, gluten, soy protein, zein, etc.); algae materials; alginate; etc., as well as combinations of these. For example, starch is a biopolymer composed of amylose and amylopectin. Amylose is practically a linear polymer having a molecular weight in the range of 100,000-500,000, while amylopectin is a highly branched polymer having a molecular weight of up to several million. Although starch is produced in many plants, typical sources include the seeds of cereal grains, such as corn, waxy corn, wheat, sorghum, rice, and waxy rice; tubers like the potato; roots, such as tapioca (that is, cassava and yucca), sweet potato, and arrowroot; and the sago marrow.

In general terms, any natural (unmodified) and / or modified starch can be employed in the present invention. Modified starches, for example, which are frequently used are chemically modified by typical processes known in the art (for example, esterification, etherification, oxidation, acid hydrolysis, enzymatic hydrolysis, etc.). The ethers and / or starch esters may be particularly desirable, such as hydroxyalkyl starches, carboxymethyl starches, and the like. The hydroxyalkyl group of the hydroxyalkyl starches may contain, for example, 1 to 10 carbon atoms, in some Modes of 1 to 6 carbon atoms, in some embodiments of 1 to 4 carbon atoms, and in some embodiments, of 2 to 4 carbon atoms. Representative hydroxyalkyl starches are hydroxyethyl starch, hydroxypropyl starch, hydroxybutyl starch, and their derivatives. Starch esters, for example, can be prepared by use of a wide variety of anhydrides (eg, acetic, propionic, butyric, etc.), organic acids, acid chlorides, or other esterification reagents. The degree of esterification can vary as desired, such as from 1 to 3 ester groups per glucosidic unit of the starch.

Regardless of whether it is in a native or modified form, the starch may contain different percentages of amylose and amylopectin, different sizes of the starch granules and different polymer weights for amylose and amylopectin. The high amylose starches contain more than about 50% by weight of amylose and the low amylose starches contain less than about 50% by weight of amylose. Although not necessary, low amylose starches having an amylose content of from about 10% to about 40% by weight, and in some embodiments, from about 15% to about 35% by weight, are particularly suitable for use in the present invention. Examples of such low amylose starches include corn starch and potato starch, both of which have an amylose content of approximately 20% by weight. Such low amylose starches typically have a number average molecular weight ("Mn") in the range of about 50,000 to about 1,000,000 grams per mole, in some embodiments from about 75,000 to about 800,000 grams per mole, and in some embodiments, about 100,000 to about 600,000 grams per mole, as well as a weighted average molecular weight ("Mw") in the range of about 5,000,000 to about 25,000,000 grams per mole, in some embodiments from about 5,500,000 to about 15,000,000 grams per mole, and in some modes, from approximately 6,000,000 to approximately 12,000,000 grams per mole. In addition, the ratio of the weight average molecular weight to the number average molecular weight ("Mw / Mn", ie the "polydispersity index") is relatively high, for example, the polydispersity index may be in the range of about 20 to about 100. The weighted and numerical average molecular weights can be determined by methods known to those skilled in the art.

B. Plasticizer As indicated above, a liquid plasticizer is further employed in the thermoplastic composition to help make the biopolymer processable by melting. For example, there are usually starches in the form of granules that have an outer coating or membrane that encapsulates the more water soluble amylose and amylopectin chains within the interior of the granule. When heated, polar solvents ("plasticizers") can soften and penetrate the outer membrane and cause the starch chains inside to absorb water and swell. This swelling will cause, at some point, that the outer layer will break and will result in an irreversible breakdown of the structure of the starch granule. Once the structure is broken, the chains of the starch polymer containing amylose and amylopectin polymers, which are initially compressed within the granules, will stretch and form a generally messy crosslinking of the polymer chains. After resolidification, however, the chains can be reoriented to form crystalline or amorphous solids having variable resistances depending on the orientation of the starch polymer chains. Because starch (natural or modified) is thus capable of melting and resolidifying, it is generally considered a "thermoplastic starch." Suitable liquid plasticizers may include, for example, polyhydric alcohol plasticizers, such as sugars (eg, glucose, sucrose, fructose, raffinose, maltodextrose, galactose, xylose, maltose, lactose, mannose, and erythrose), sugar alcohols ( for example, erythritol, xylitol, malitol, mannitol, glycerol (or glycerin), and sorbitol), polyols (for example, ethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, and hexanetriol), and the like. Also suitable are organic compounds that form hydrogen bonds that do not have a hydroxyl group, including urea and urea derivatives; anhydrides of sugar alcohols such as sorbitan; animal proteins such as gelatin; vegetable proteins such as sunflower protein, soy proteins, cottonseed proteins; and mixtures of these. Other suitable plasticizers may include the esters of phthalate, dimethyl and diethyl succinate and the related esters, glycerol triacetate, glycerol monoacetates and diacetates, glycerol mono-, di-, and tripropionates, butanoates, stearates, lactic acid esters, citric acid, adipic acid esters, stearic acid esters, oleic acid esters, and other acid esters. In addition, aliphatic acids such as ethylene acrylic acid, ethylene maleic acid, acrylic butadiene acid, maleic butadiene acid, acrylic propylene acid, maleic propylene acid, and other hydrocarbon-based acids can be used. A low molecular weight plasticizer, such as less than about 20,000 g / mol, preferably less than about 5,000 g / mol and more preferably less than about 1,000 g / mol is preferred.

The relative amount of biopolymers and plasticizers employed in the thermoplastic composition may vary depending on a variety of factors, such as the molecular weight of the biopolymer, the type of biopolymer (eg, modified or unmodified), the affinity of the plasticizer with the biopolymer, and so on. Typically, however, the weight ratio of the biopolymers to the plasticizers is from about 1 to about 10, in some embodiments from about 1.5 to about 8, and in some embodiments, from about 2 to about 6. For example, the biopolymers may comprise from about 5 wt% to about 50 wt%, in some embodiments from about 10 wt% to about 40 wt%, and in some embodiments, from about 15 wt% to about 30 wt% of the composition, while the plasticizer may constitute from about 0.5% by weight to about 20% by weight, in some embodiments from about 1% by weight to about 15% by weight, and in some embodiments, from about 5% by weight to about 10% by weight of the composition. It should be understood that the weight of the biopolymers referred to herein includes any water bound naturally occurring in the starch before mixing it with other components to form the thermoplastic starch. Starches, for example, typically have a bound water content of about 5% to 16% by weight of the starch.

C. Polyolefin As indicated above, a polyolefin is also used in the film. Among other things, the polyolefin helps counteract the rigidity of the biopolymer, which thereby improves the ductility and melt processability of the film. Such polyolefins are typically employed in an amount of about 10% by weight to about 50% by weight, in some embodiments from about 20% by weight to about 45% by weight, and in some embodiments, from about 25% by weight to about 40% by weight of the polymer content of the thermoplastic composition.

Exemplary polyolefins for this purpose may include, for example, polyethylene, polypropylene, mixtures and copolymers thereof. In a particular embodiment, a polyethylene is used which is a copolymer of ethylene and an α-olefin, such as a C3-C2o α-olefin or C3-Ci2 α-olefin. Suitable α-olefins can be linear or branched (eg, one or more Ci-C3 alkyl branches, or an aryl group). Specific examples include 1-butene, 3-methyl-1-butene; 3, 3-dimethyl-1-butene; 1-pentene; 1-pentene with one or more methyl, ethyl or propyl substituents; 1-hexene with one or more methyl, ethyl or propyl substituents; 1-heptene with one or more methyl, ethyl or propyl substituents; 1-octene with one or more methyl, ethyl or propyl substituents; 1-nonene with one or more methyl, ethyl or propyl substituents; 1-decene ethyl, methyl or dimethyl-substituted; 1-dodecene; and styrene. Particularly desired α-olefin comonomers are 1-butene, 1-hexene and 1-octene. The ethylene content of such copolymers can be from about 60 mole to about 99 mole%, in some embodiments from about 80 mole% to about 98.5 mole%, and in some embodiments, from about 87 mole% to approximately 97.5% in moles. The α-olefin content may also be in the range of about 1 mole% to about 40 mole%, in some embodiments from about 1.5 mole% to about 15 mole%, and in some embodiments, about 2.5% in moles to approximately 13% in moles.

The density of polyethylene can vary depending on the type of polymer used, but generally ranges from 0.85 to 0.96 grams per cubic centimeter ("g / cm3"). Polyethylene "plastomers", for example, can have a density in the range of 0.85 to 0.91 g / cm 3. Similarly, "linear low density polyethylene" (LLDPE) can have a density in the range of 0.91 to 0.940 g / cm3; "Low density polyethylene" (LDPE) may have a density in the range of 0.910 to 0.940 g / cm3, and "high density polyethylene" (HDPE) may have a density in the range of 0. 940 to 0.960 g / cm3. Densities can be measured in accordance with ASTM 1505. Ethylene-based polymers particularly suitable for use in the present invention may be available under the designation EXACT ™ from ExxonMobil Chemical Company of Houston, Texas. Other suitable polyethylene plastomers are available under the designation ENGAGE ™ and AFFINITY ™ from the Dow Chemical Company of Midland, Michigan. Still other suitable ethylene polymers are available from The Dow Chemical Company under the designations DOWLEX ™ (LLDPE) and ATTANE ™ (ULDPE). Other suitable ethylene polymers are described in U.S. Pat. 4,937,299 to Ewen et al .; 5,218,071 to Tsutsui et al .; 5,272,236 to Lai, et al .; and 5,278,272 to Lai, and others, which are hereby incorporated by reference in their entirety for all purposes.

Of course, the present invention is in no way limited to the use of ethylene polymers. For example, propylene polymers may also be suitable for use as a semicrystalline polyolefin. Suitable propylene polymers may include, for example, polypropylene homopolymers, as well as copolymers or terpolymers of propylene with an α-olefin (eg, C3-C2o), such as ethylene, 1-butene, 2-butene, the various isomers of pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-unidecene, 1-dodecene, 4-methyl-1-pentene, 4-methyl-1-hexene, 5-methyl-1- hexene, vinylcyclohexene, styrene, etcetera. The comonomer content of the propylene polymer can be about 35% by weight or less, in some embodiments from about 1% by weight to about 20% by weight, and in some embodiments, from about 2% by weight to about 10% in weigh. The density of the polypropylene (for example, propylene / -olefin copolymer) can be 0.95 grams per cubic centimeter (g / cm3) or less, in some embodiments, from 0.85 to 0.92 g / cm3, and in some embodiments, 0.85 g / cm3 to 0.91 g / cm3. Suitable propylene polymers are commercially available under the designations VISTAMAXX ™ from ExxonMobil Chemical Co. from Houston, Texas; FINA ™ (for example, 8573) from Atofina Chemicals de Feluy, Belgium; TAFMER ™ available from Mitsui Petrochemical Industries; and VERSIFY ™ available from Dow Chemical Co. of Midland, Michigan. Other examples of suitable propylene polymers are described in U.S. Pat. 6,500,563 from Datta, and others; 5,539,056 of Yang, and others; and 5,596,052 to Resconi, and others, which are hereby incorporated by reference in their entirety for all purposes.

Generally, any of a variety of known techniques for forming polyolefins can be employed. For example, olefin polymers can be formed using a free radical catalyst or a coordination catalyst (eg, Ziegler-Natta or metallocene catalysts). The metallocene catalyzed polyolefins, for example, in U.S. Patent Nos. 5,571,619 to McAlpin et al .; 5,322,728 to Davis et al .; 5,472,775 to Obijeski et al .; 5,272,236 to Lai et al .; and 6,090,325 Wheat, and others, which are hereby incorporated by reference in their entirety for all purposes.

The flow index (MI) of polyolefins can vary generally, but typically ranges from about 0.1 grams per 10 minutes to about 100 grams per 10 minutes, in some embodiments from about 0.5 grams per 10 minutes to about 30 grams per 10 minutes, and in some modalities, approximately 1 to approximately 10 grams per 10 minutes, determined at 190 ° C. The flow index is the weight of the polymer (in grams) that can be forced through an orifice of the 20 cm extrusion rheometer (diameter of 0.0825 inches) when subjected to a force of 2160 grams in 10 minutes at 190 ° C, and can be determined in accordance with Test Method ASTM D1238-E.

D. Compatibilizer To improve the compatibility and dispersion characteristics of the biopolymers and polyolefins, a compatibilizer is used in the thermoplastic composition. Typically, the compatibilizer constitutes from about 0.1 wt% to about 15 wt%, in some embodiments about 0.5% by weight to about 10% by weight, and in some embodiments, from about 1% by weight to about 5% by weight of the composition. The compatibilizer generally has a polar component provided by one or more functional groups that are compatible with the biopolymer and a non-polar component provided by an olefin that is compatible with the polyolefin. The olefin component of the compatibilizer can generally be formed of any linear or branched α-olefin monomer, oligomer, or polymer (including copolymers) derived from an olefin monomer. For example, the compatibilizer may include polyethylene-co-vinyl acetate (EVA), polyethylene-co-vinyl alcohol (EVOH), polyethylene-co-acrylic (EAA), etc. where the olefin component is provided by the main chain of polyethylene. In other embodiments, the olefin component can be formed from an α-olefin monomer, which typically has from 2 to 14 carbon atoms and preferably from 2 to 6 carbon atoms. Examples of suitable monomers include, but are not limited to, ethylene, propylene, butene, pentene, hexene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, and 5-methyl. -l-hexene. Examples of polyolefins include both homopolymers and copolymers, ie, polyethylene, ethylene copolymers such as MEPD, polypropylene, propylene copolymers, and polymethylpentene polymers. A copolymer of olefin may include a lesser amount of non-olefinic monomers, such as styrene, vinyl acetate, diene, or acrylic and non-acrylic monomers. The functional groups can be incorporated into the polymer backbone using a variety of known techniques. For example, a monomer containing the functional group can be grafted onto a polyolefin backbone to form a graft copolymer. Such grafting techniques are well known in the art and are described, for example, in U.S. Pat. 5,179,164. In other embodiments, the monomer containing the functional groups can be copolymerized with an olefin monomer to form a block or random copolymer.

Regardless of the manner in which it is incorporated, the functional group of the compatibilizer can be any group that provides a polar segment to the molecule, such as a carboxyl group, an acid anhydride group, an amide group, an imide group, a group carboxylate, an epoxy group, an amino group, an isocyanate group, a group having an oxazoline ring, a hydroxyl group, and the like. Polyolefins modified with maleic anhydride are particularly suitable for use in the present invention. Such modified polyolefins are typically formed by grafting maleic anhydride onto a polymeric backbone material. Such maleated polyolefins are available from E.I. du Pont de Nemours and Company under the designation FUSABOND®, such as Series P (chemically modified polypropylene), Series E (chemically modified polyethylene), Series C (chemically modified ethylene vinyl acetate), Series A (ethylene acrylate or chemically modified copolymers or terpolymers), or Series N (ethylene-propylene, ethylene-propylene-diene monomer ("EPDM") or chemically modified ethylene-octene). Alternatively, the maleated polyolefins are furthermore available from Chemtura Corp. under the designation Polybond® and from Eastman Chemical Company under the designation Eastman G series, and AMPLIFY ™ GR Functional Polymers (polyolefins grafted with maleic anhydride). In a particular embodiment, the compatibilizer is a polyethylene-maleic anhydride graft copolymer having the structure shown below: The cyclic anhydride at one end is chemically bonded directly to the polyethylene chain. In one embodiment, the polar anhydride group of the molecule can be associated with the hydroxyl groups of a starch biopolymer through hydrogen bonds and polar-polar molecular interactions and a chemical reaction to form an ester bond during the melt extrusion process . The hydroxyl of the starch is they will undergo an esterification reaction with the anhydride to achieve an opening reaction of the ring to chemically bind the starch polymer to the maleic anhydride of the grafted polyethylene. This reaction is carried out under the high temperatures and pressures of the extrusion process.

E. Additional biodegradable polymer Generally speaking, most of the polymers used in the composition are biodegradable polymers. For example, from about 50% by weight to about 90% by weight, in some embodiments from about 55% by weight to about 80% by weight, and in some embodiments, from about 60% by weight to about 75% by weight of The polymers used in the composition are biodegradable polymers. In one embodiment, for example, substantially all biodegradable polymers are renewable biopolymers, as described above. Alternatively, however, other types of biodegradable polymers can be further employed to help further improve the ability to melt process the thermoplastic composition. In such embodiments, the additional biodegradable polymers may be from about 10 wt% to about 70 wt%, in some embodiments from about 20 wt% to about 60 wt%, and in some embodiments, about 30 wt% to about 50% by weight of the polymer content of the thermoplastic composition, while the biopolymers may also constitute from about 1% by weight to about 35% by weight, in some embodiments from about 5% by weight to about 30% by weight, and in some embodiments, from about 10% by weight to about 25% by weight of the polymer content of the thermoplastic composition.

A particularly suitable type of biodegradable polymer that can be used together with the biopolymer is a biodegradable polyester. Such biodegradable polyesters typically have a low glass transition temperature ("Tg") to reduce the stiffness of the film and improve the processability of the polymers. For example, the Tg may be about 25 ° C or less, in some embodiments about 0 ° C or less, and in some embodiments, about -10 ° C or less. Likewise, the melting point of the biodegradable polyesters is also relatively low to improve the rate of biodegradation. For example, the melting point is typically from about 50 ° C to about 180 ° C, in some embodiments from about 80 ° C to about 160 ° C, and in some embodiments, from about 100 ° C to about 140 ° C. The melting temperature and vitreous transition temperature can be determined by the use of differential scanning calorimetry (DSC) according to ASTM D-3417 as is well known in the art. Such tests can be used using a differential scanning calorimeter THER AL ANALYST 2910 (equipped with a liquid nitrogen cooling accessory) and with a THERMAL ANALYST 2200 analysis software (version 8.10), which is available from TA Instruments Inc. of New Castle, Delaware.

The biodegradable polyesters may also have a number average molecular weight ("Mn") in the range of about 40,000 to about 120,000 grams per mole, in some embodiments from about 50,000 to about 100,000 grams per mole, and in some embodiments, from about 60,000 to about 85,000 grams per mole. Likewise, the polyesters may further have a weight average molecular weight ("Mw") in the range of about 70,000 to about 240,000 grams per mole, in some embodiments from about 80,000 to about 190,000 grams per mole, and in some embodiments, of about 100,000 to approximately 150,000 grams per mole. The ratio between the weight average molecular weight to the number average molecular weight ("Mw / Mn"), ie the "polydispersity index", is also relatively low. For example, the polydispersity index typically ranges from about 1.0 to about 4.0, in some embodiments from about 1.2 to about 3.0, and in some embodiments, from about 1.4 to about 2.0. The pesos Molecular weights and number can be determined by methods known to those skilled in the art.

The biodegradable polyesters may also have an apparent viscosity of about 100 to about 1000 Pascal seconds (Pa-s), in some embodiments from about 200 to about 800 Pa-s, and in some embodiments, from about 300 to about 600 Pa-s , determined at a temperature of 170 ° C and a shear rate of 1000 sec. "1. The flow rate of the biodegradable polyesters may also be in the range of about 0.1 to about 10 grams per 10 minutes, in some embodiments of about 0.5 to about 8 grams per 10 minutes, and in some embodiments, from about 1 to about 5 grams per 10 minutes The melt index is the weight of a polymer (in grams) that can be forced through an extrusion rheometer hole 20 cm (diameter of 0.0825 inches) when subjected to a load of 2160 grams in 10 minutes at a certain temperature (for example, 190 ° C ), measured in accordance with Test Method ASTM D1238-E.

Of course, the flow rate of the biodegradable polyesters will ultimately depend on the selected film formation process. For example, when they are extruded as a cast film, the higher melt index polymers are typically desired, such as about 4 grams per 10 minutes or greater, in some embodiments, from about 5 to about 12 grams per 10 minutes, and in some embodiments, from about 7 to about 9 grams per 10 minutes. Likewise, when formed as a blown film, lower melt index polymers are typically desired, such as less than about 12 grams per 10 minutes or less, in some embodiments from about 1 to about 7 grams per 10 minutes, and in some embodiments, from about 2 to about 5 grams per 10 minutes.

Examples of suitable biodegradable polyesters include aliphatic polyesters, such as polycaprolactone, polyesteramides, modified polyethylene terephthalate, polylactic acid (PLA) and its copolymers, terpolymers based on polylactic acid, polyglycolic acid, polyalkylene carbonates (such as polyethylene carbonate) , polyhydroxyalkanoates (PHA), poly-3-hydroxybutyrate (PHB), poly-3-hydroxyvalerate (PHV), poly-3-hydroxybutyrate-co-4-hydroxybutyrate, copolymers of poly-3-hydroxybutyrate-co-3-hydroxyvalerate ( PHBV), poly-3-hydroxybutyrate-co-3-hydroxyhexanoate, poly-3-hydroxybutyrate-co-3-hydroxyoctanoate, poly-3-hydroxybutyrate-co-3-hydroxydocanoate, poly-3-hydroxybutyrate-co-3-hydroxyoctadecanoate , and aliphatic polymers based on succinate (for example, polybutylene succinate, polybutylene adipate succinate, succinate polyethylene, etc.); aromatic polyesters and modified aromatic polyesters; and aliphatic-aromatic copolyesters. In a particular embodiment, the biodegradable polyester is an aliphatic-aromatic copolyester (eg, block, random, graft, etc.). The aliphatic-aromatic copolyester can be synthesized using any known technique, such as through the condensation polymerization of a polyol together with aliphatic and aromatic dicarboxylic acids or anhydrides thereof. The polyols can be substituted or unsubstituted, linear or branched, polyols selected from polyols containing 2 to about 12 carbon atoms and polyalkylene glycol ethers containing 2 to 8 carbon atoms. Examples of polyols that can be used include, but are not limited to, ethylene glycol, diethylene glycol, propylene glycol, 1,2-propanediol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,2-butane diol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,6-hexanediol, polyethylene glycol, diethylene glycol, 2,2,4-trimethyl-1,6-hexanediol, thiodiethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, cyclopentanediol, triethylene glycol, and tetraethylene glycol. Preferred polyols include 1,4-butanediol; 1,3-propanediol; ethylene glycol; 1,6-hexanediol; diethylene glycol; and 1,4-cyclohexanedimethanol.

The representative aliphatic dicarboxylic acids that they can be used include the linear or branched substituted or unsubstituted, non-aromatic dicarboxylic acids, selected from aliphatic dicarboxylic acids containing 1 to about 10 carbon atoms, and derivatives thereof. Non-limiting examples of aliphatic dicarboxylic acids include malonic, malic, succinic, oxalic, glutaric, adipic, pimelic, azelaic, fumaric sebacic, 2,2-dimethyl glutaric, suberic, 1,3-cyclopentanedicarboxylic, 1,4-cyclohexanedicarboxylic, 1,3-cyclohexanedicarboxylic, diglycolic, itaconic, maleic, and 2,5-norbornanedicarboxylic. Representative aromatic dicarboxylic acids which may be used include the substituted or unsubstituted, linear or branched aromatic dicarboxylic acids, selected from aromatic dicarboxylic acids containing 1 to about 6 carbon atoms, and derivatives thereof. Non-limiting examples of aromatic dicarboxylic acids include terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalate, 2,6-naphthalene dicarboxylic acid, dimethyl-2,6-naphthalate, 2,7-naphthalene dicarboxylic acid, dimethyl-2, 7-naphthalate, 3,4'-diphenyl ether dicarboxylic acid, dimethyl-3,4'-diphenyl ether dicarboxylate, 4,4'-diphenyl ether dicarboxylic acid, dimethyl-4,4'-diphenyl ether dicarboxylate, 3,4 'acid -diphenyl dicarboxylic sulfide, dimethyl-3,4-dicarboxylic acid diphenyl sulfide, 4,4'-diphenyl sulficarboxylic acid, dimethyl-4,4'-diphenyl sulfur dicarboxylate, 3,4'-diphenyl sulfone dicarboxylic acid, dimethyl-3,31-diphenyl sulfone dicarboxylate, 4,4'-diphenyl sulfone dicarboxylic acid, dimethyl-, 41-diphenyl sulfone dicarboxylate, 3,4-benzophenoneadicarboxylic acid, dimethyl -3,41 -benzophenoneadicarboxylate, 4,4'-benzophenoneadicarboxylic acid, dimethyl-4, '-benzophenoneadicarboxylate, 1,4-naphthalene dicarboxylic acid, dimethyl-1,4-naphthalate, 4,4'-methylene bis (benzoic acid) , dimethyl-4,41-methylene bis (benzoate), et cetera, and mixtures thereof.

The polymerization can be catalyzed by a catalyst, such as a titanium-based catalyst (for example, tetraisopropyl titanate, tetraisopropoxy titanium, dibutoxydiacetoacetoxy titanium, or tetrabutyl titanate). If desired, a diisocyanate chain extender can be reacted with the copolyester to increase its molecular weight. Representative diisocyanates may include toluene 2,4-diisocyanate, toluene 2,6-diisocyanate, 2,4'-diphenylmethane diisocyanate, naphthylene-1, 5-diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate ("HMDI"), diisocyanate isophorone and methylene bis (2-isocyanatocyclohexane). In addition, trifunctional isocyanate compounds containing isocyanurate and / or biurea groups having a functionality of not less than three, or partially replacing the diisocyanate compounds with tri-or polyisocyanates. The preferred diisocyanate is hexamethylene diisocyanate. The amount of chain extender used is typically from about 0.3 to about 3.5% by weight, in some embodiments, from about 0.5 to about 2.5% by weight based on the total weight percentage of the polymer.

The copolyesters can be a linear polymer or a long chain branched polymer. The long chain branched polymers are generally prepared by the use of a low molecular weight branching agent, such as a polyol, a polycarboxylic acid, a hydroxy acid, and the like. Representative low molecular weight polyols that can be employed as branching agents include glycerol, trimethylolpropane, trimethylolethane, polyether triols, 1,2,4-butanetriol, pentaerythritol, 1,2,6-hexanetriol, sorbitol, 1, 1, 4, 4, -tetrakis (hydroxymethyl) cyclohexane, tris (2-hydroxyethyl) isocyanurate, and dipentaerythritol. Representative high molecular weight polyols (molecular weight of 400 to 3000) which can be used as branching agents include triols derived from the condensation of alkylene oxides having 2 to 3 carbons, such as ethylene oxide and propylene oxide with initiators of polyol. Representative polycarboxylic acids which can be used as branching agents include hemimellitic acid, trimellitic acid (1, 2, 4-benzenetricarboxylic acid) and anhydride, trimesic acid (1, 3, 5-benzenetricarboxylic acid), pyromellic acid and anhydride, benzenetetracarboxylic acid, benzophenone tetracarboxylic acid, 1,1,2,2-ethane-tetracarboxylic acid, 1,1-ethano-tricarboxylic acid, 1,3 acid, 5-pentanotricarboxílico, and 1, 2, 3, 4-ciclopentanotetracarboxílico acid. Representative hydroxy acids that can be used as branching agents include malic acid, citric acid, tartaric acid, 3-hydroxyglutaric acid, mucic acid, trihydroxyglutaric acid, 4-carboxylic anhydride, hydroxy isophthalic acid, and 4- (beta-hydroxyethyl) phthalic acid. . Such hydroxy acids contain a combination of 3 or more hydroxyl and carboxyl groups. Especially preferred branching agents include trimellitic acid, trimesic acid, pentaerythritol, trimethylol propane and 1,2,4-butanetriol.

The aromatic dicarboxylic acid monomer constituent may be present in the copolyester in an amount of about 10 mol% to about 40 mol%, in some embodiments from about 15 mol% to about 35 mol%, and in some embodiments , from about 15 mol% to about 30 mol%. The aliphatic dicarboxylic acid monomer constituent may also be present in the copolyester in an amount of about 15 mol% to about 45 mol%, in some embodiments from about 20 mol% to about 40 mol%, and in some embodiments modalities, of about 25 mol% to about 35 mol%. The polyol monomer component can also be present in the aliphatic-aromatic copolyester in an amount of from about 30 mol% to about 65 mol%, in some embodiments from about 40 mol% to about 50 mol%, and in some embodiments, from about 45% mol to about 55% mol.

In a particular embodiment, for example, the aliphatic-aromatic copolyester may comprise the following structure: where, m is an integer from 2 to 10, in some modalities from 2 to 4, and in one modality, 4; n is an integer from 0 to 18, in some modalities from 2 to 4, and in one modality, 4; p is an integer from 2 to 10, in some modalities from 2 to 4, and in one modality, 4; x is an integer greater than 1; and y is an integer greater than 1.

An example of such a copolyester is polybutylene adipate terephthalate, which is commercially available under the designation ECOFLEX® F BX 7011 from BASF Corp. Another example of A suitable copolyester containing a monomer constituent of aromatic terephthalic acid is available under the designation ENPOL ™ 8060 from IRE Chemicals (South Korea). Other suitable aliphatic-aromatic copolyesters can be described in U.S. Pat. 5,292,783; 5,446,079; 5,559,171; 5,580,911; 5,599,858; 5,817,721; 5,900,322; and 6,258,924, which are hereby incorporated by reference in their entirety for all purposes.

F. Other additives In addition to the components mentioned above, still other additives can be incorporated into the composition further, such as melt stabilizers, dispersion aids (e.g., surfactants), process stabilizers, thermal stabilizers, light stabilizers, antioxidants, aging stabilizers. by heat, whitening agents, antiblocking agents, bonding agents, lubricants, fillers, etcetera. For example, the film may include a mineral filler, such as talc, calcium carbonate, magnesium carbonate, clay, silica, alumina, boron oxide, titanium oxide, cerium oxide, germanium oxide, and the like. The film containing the filler can be stretched to form permeable films. When employed, the mineral filler (s) typically constitutes (s) from about 0.01% by weight to about 40% by weight, in some embodiments from about 0.1% by weight to about 30% by weight, and in some embodiments, from about 0.5% by weight to about 20% by weight of the thermoplastic composition.

The dispersion aids can, for example, be used to help create a uniform dispersion of the biopolymer / plasticizer and retard or prevent separation of the mixture in the constituent phases. When employed, the dispersing aid (s) typically constitutes (s) from about 0.01% by weight to about 10% by weight, in some embodiments from about 0.1% by weight to about 5% by weight , and in some embodiments, from about 0.5% by weight to about 4% by weight of the thermoplastic composition. Although any dispersion aid can generally be employed in the present invention, surfactants having a determined hydrophilic / lipophilic balance ("HLB") can improve the long-term stability of the composition. The HLB index is well known in the art and is a scale that measures the balance between the hydrophilic and lipophilic tendencies of a compound in solution. The HLB scale is in the range of 1 to about 50, with the lower numbers representing highly lipophilic trends and the higher numbers representing highly hydrophilic trends. In some embodiments of the present invention, the HLB value of the surfactants is from about 1 to about 20, in some embodiments from about 1 to about 15 and in some embodiments, from about 2 to about 10. If desired, two or more surfactants having HLB values below or above may be employed. of the desired value, but that together have an average value of HLB within the desired range.

One class of surfactants particularly suitable for use in the present invention is that of nonionic surfactants, which typically have a hydrophobic base (eg, a long-chain alkyl group or an alkylated aryl group) and a hydrophilic chain (e.g. a chain containing ethoxy and / or propoxy moieties). For example, some suitable nonionic surfactants that may be used include, but are not limited to, ethoxylated alkylphenols, ethoxylated and propoxylated fatty alcohols, polyethylene glycol methyl glucose ethers, polyethylene glycol ethers of sorbitol, block copolymers of ethylene oxide-oxide. propylene, ethoxylated esters of fatty acids (C8-Ci8), condensation products of ethylene oxide with long-chain amines or amides, condensation products of ethylene oxide with alcohols, fatty acid esters, monoglyceride or diglycerides of chain alcohols long, and mixtures of these. In a particular embodiment, the nonionic surfactant can be a fatty acid ester, such as a fatty acid ester of sucrose, a fatty acid ester of glycerol, a fatty acid ester of propylene glycol, a fatty acid ester of sorbitan, a fatty acid ester of pentaerythritol, a fatty acid ester of sorbitol, and the like. The fatty acid used to form such esters can be saturated or unsaturated, substituted or unsubstituted, and can contain from 6 to 22 carbon atoms, in some embodiments from 8 to 18 carbon atoms, and in some embodiments, from 12 to 14 atoms of carbon. In a particular embodiment, mono- and di-glycerides of fatty acids can be used in the present invention.

II. Extrusion by fusion As indicated above, the thermoplastic composition of the present invention is formed by melt blending a biopolymer, a plasticizer, a polyolefin, and a compatibilizer together within an extruder. More particularly, the polymer components can be supplied separately or together to a feed section of the extruder (eg, the hopper) and the liquid plasticizer can be injected directly into the extruder at the same location, or at a location downstream thereof. Although it is not precomposed with the plasticizer before being fed into the extruder, the present inventors have discovered that the biopolymer can still be easily processed. In this way, the pre-encapsulation or precomposition stages of the plasticizer and the biopolymer are not required. expensive and time consuming.

With reference to Fig. 1, for example, an embodiment of an extruder 80 is illustrated that can be used for this purpose. As shown, the extruder 80 contains a housing or cylinder 114 and a screw 120 (e.g., barrier screw) rotatably driven at one end by a suitable drive unit 124 (typically including a motor and a gearbox). ). If desired, a twin screw extruder containing two separate screws can be used. The extruder 80 generally contains three sections: the feed section 132, the melting section 134, and the mixing section 136. The feeding section 132 is the inlet portion of the cylinder 114 where the polymeric material is added. The melting section 134 is the section of phase change in which the plastic material changes from a solid to a liquid. The mixing section 136 is adjacent to the exit end of the cylinder 114 and is the portion in which the liquid plastic material is completely mixed. Although there is no precisely defined delineation of these sections when manufacturing the extruder, it is well within the experience of those skilled in the art to reliably identify the melting section 134 of the extruder cylinder 114 in which the extruder is being produced. phase change from solid to liquid. a hopper 40 is further located adjacent to the unit drive 124 for supplying the biopolymer, the polyolefin, and / or other materials through an opening 142 in the cylinder 114 to the feed section 132. Opposed to the drive unit 124 is the output end 144 of the extruder 80, where the extruded plastic leaves for further processing to form a film, which will be described in more detail below. In the extruder barrel 114 there is further provided a plasticizer supply station 150 which includes at least one hopper 154, which is attached to a pump 160 to selectively deliver the plasticizer through an aperture 162 to the melting section 134. this way, the plasticizer can be mixed with the polymers in a consistent and uniform manner. Of course, in addition to or instead of supplying the plasticizer to the melting section 134, it should further be understood that it can be supplied to other sections of the extruder, such as the feed section 132 and / or the mixing section 136. For example, in certain embodiments, the plasticizer can be injected directly into the hopper 40 together with other polymeric materials.

The pump 160 may be a high pressure pump (e.g., a positive displacement pump) with an injection valve so as to provide a fixed selected amount of plasticizer to the cylinder 114. If desired, a logic controller may also be employed. programmable 170 for connecting the drive unit 124 to the pump 160 so as to provide a selected volume of plasticizer based on the speed of the drive unit of the screw 120. That is, the controller 170 can control the rotation speed of the screw the drive unit 120 and the pump 160 for injecting the plasticizer at a speed based on the rotation speed of the screw. Accordingly, if the rotation speed of the screw 120 is increased to drive larger amounts of plastic through the cylinder 114 in a given time unit, the pumping speed of the pump 160 can be similarly increased to proportionally pump larger quantities of plasticizer to cylinder 114.

The plasticizer and the polymer components can be processed within the extruder 80 under shear and pressure and heat conditions to ensure sufficient mixing. For example, the melting process can occur at a temperature from about 75 ° C to about 280 ° C, in some embodiments, from about 100 ° C to about 250 ° C, and in some embodiments, from about 150 ° C to about 200 ° C. C. Likewise, the apparent shear rate during the melting process may be in the range of about 100 seconds "1 to about 10,000 seconds" 1, in some embodiments of about 500 seconds "1 to about 5000 seconds "1, and in some modes, from approximately 800 seconds" 1 to approximately 1200 seconds "1. The apparent shear rate is equal to 4Q / nR3, where Q is the volumetric flow velocity (" m3 / s ") of the melt of the polymer and R is the radius ("m") of the capillary (eg, the die of the extruder) through which the molten polymer flows.

Once processed in the extruder, the melt-mixed composition can flow through a die to form an extruded product that is in the form of a strand, canvas, film, and so on. If desired, the extruded product can optionally be cooled using any of a variety of techniques. In one embodiment, for example, the extruded product is cooled off the die using a multi-stage system that includes at least one step of cooling with water and at least one step of air cooling. For example, the extruded product may initially be contacted with water for a certain period of time so that it is partially cooled. The actual water temperature and the total time that is in contact with the extruded product can vary depending on the extrusion conditions, the size of the extruded product, and so on. For example, the water temperature is typically from about 10 ° C to about 60 ° C, in some embodiments from about 15 ° C to about 40 ° C, and in some embodiments, from about 20 ° C to about 30 ° C. Likewise, the total time the water is in contact with the extruded product (or dwell time) is typically little, such as from about 1 to about 10 seconds, in some embodiments from about 2 to about 8 seconds, and in some embodiments , from about 3 to about 6 seconds. If desired, multiple stages of cooling with water can be employed to achieve the desired degree of cooling. Regardless of the number of stages employed, the extruded product cooled with water is typically at a temperature of about 40 ° C to about 100 ° C, in some embodiments from about 50 ° C to about 80 ° C, and in some embodiments, about 60 ° C to about 70 ° C, and contains water in an amount of about 2,000 to about 50,000 parts per million ("ppm"), in some embodiments from about 4,000 to about 40,000 ppm, and in some embodiments, of about 5,000 at approximately 30,000 ppm.

After the water cooling step (s), the extruded product is further subjected to at least one air cooling step in which a stream of air is placed in contact with the extruded product. The temperature of the air stream can vary depending on the temperature and the moisture content of the extruded product cooled with water, but is typically from about 0 ° C to about 40 ° C, in some embodiments from about 5 ° C to about 35 ° C, and in some embodiments, from about 10 ° C to about 30 ° C. If desired multiple air cooling stages can be employed to achieve the desired degree of cooling. Regardless of the number of stages employed, the total time the air is in contact with the extruded product (or residence time) is typically little, such as from about 1 to about 50 seconds, in some embodiments from about 2 to about 40. seconds, and in some modalities, from about 3 to about 35 seconds. The resultant air-cooled extruded product is generally free of water and has a low moisture content, such as from about 500 to about 20,000 parts per million ("ppm"), in some embodiments from about 800 to about 15,000 ppm, and in some embodiments, from about 1,000 to about 10,000 ppm. The temperature of the extruded product cooled with air may be further from about 15 ° C to about 80 ° C, in some embodiments from about 20 ° C to about 70 ° C, and in some embodiments, from about 25 ° C to about 60 ° C. C.

The specific configuration of the multi-stage cooling system can vary as it will be understood by those with experience in the matter. With reference to Fig. 2, for example, one mode of the cooling system 200 is shown in more detail. In this particular configuration, the cooling system 200 employs a single stage of cooling with water which involves the use of a liquid water bath 208 and furthermore a single air cooling step involving the use of an air knife 210. It is understood that other diverse cooling techniques can be used in addition for each stage. For example, instead of a liquid bath, the water can be sprayed, coated, etc. on a surface of the extruded product. Likewise, other techniques for contacting the extruded product with an air stream may include fans, ovens, and so on. In any case, in the embodiment illustrated in Fig. 2, the extruded product 203 is initially immersed in the water bath 208. As noted above, the rate of cooling with water can be controlled by the temperature of the water bath 208 and the time that the extruded product 203 is immersed in the bath 208. In certain embodiments, the residence time of the extruded product 203 within the bath 208 can be adjusted by controlling the speed of the rollers 204 over which the extruded product passes through. In addition, the length "L" of the water bath 208 can also be adjusted to help achieve the desired dwell time. For example, the length of the Bath 208 may be in the range from about 1 to about 30 feet, in some embodiments from about 2 to about 25 feet, and in some embodiments, from about 5 to about 15 feet. Similarly, the length "Lx" of the water bath through which the extruded product 203 is actually submerged is typically about 0. 5 to about 25 feet, in some embodiments from about 1 to about 20 feet, and in some embodiments, from about 2 to about 12 feet. After passing through the bath 208 for the desired period of time, the resulting extruded product cooled with water 205 then passes over a series of rollers until it comes into contact with an air stream provided by the air knife 210. If desired, the air-cooled extruded product 207 can then pass through a granulator 214 to form granules for subsequent processing in the film of the present invention. Alternatively, the air-cooled extruded product 207 can be processed in the film without first forming into granules.

III. Construction of the film Any known technique can be used to form a film from the mixed and optionally cooled composition, which includes blowing, casting, flat die extrusion, and so on. In a particular mode, the movie can formed by a blowing process in which a gas (e.g., air) is used to expand a bubble of the extruded polymer mixture through an annular die. Then the bubble collapses and collects in the form of a flat film. Processes for blown film production are described, for example, in U.S. Pat. 3,354,506 from Raley; 3,650,649 of Schippers; and 3,801,429 to Schrenk et al., as well as the publication of United States patent applications no. 2005/0245162 by McCormack, et al. And 2003/0068951 by Boggs, and others, which are incorporated herein by reference in their entirety for all purposes. In yet another embodiment, however, the film is formed using a casting technique.

With reference to Fig. 3, for example, one embodiment of a method for forming a cast film is shown. In this embodiment, the raw materials (not shown) are supplied to the extruder 80 in the manner described above and shown in Fig. 1, and then are deposited on a casting roller 90 to form a monostratified precursor film 10a. If a multi-layered film is to be produced, the multiple layers are coextruded together on the casting roller 90. The casting roller 90 can optionally be provided with engraving elements to impart a pattern to the film. Typically, the casting roller 90 is maintained at a temperature sufficient to solidify and cool the canvas 10a as it is formed, such as from about 20 to 60 ° C. If desired, a vacuum box adjacent to the casting roller 90 may be placed to assist in keeping the precursor film 10a close to the surface of the roller 90. In addition, the air knives or electrostatic fasteners may help to force the film 10a against the surface of the casting roller 90 while moving around a spinning roller. An air knife is a device known in the art that centers a stream of air at a very high flow rate to hold the edges of the film.

Once melted, the film 10a can then be optionally oriented in one or more directions to further improve the uniformity of the film and reduce the thickness. The orientation can also form micropores in a film containing a charge, thus providing permeability to the film. For example, the film may be reheated immediately at a temperature below the melting point of one or more polymers in the film, but high enough to allow the composition to be dragged or stretched. In the case of the sequential orientation, the "softened" film is driven by the rollers rotating at different rotation speeds so that the canvas is stretched at the desired stretch index in the longitudinal direction (machine direction). This film oriented "uniaxially" can then laminate to a fibrous web. Additionally, the uniaxially oriented film can also be oriented in the transverse direction to the machine to form a "biaxially oriented" film. For example, the film can be fixed at its side edges by chain clips and transported in a stenter oven. In the stenter furnace, the film can be reheated and dragged in the direction transverse to the machine at the desired stretch index by separate chain clips in their forward movement.

Referring again to Fig. 3, for example, a method for forming a uniaxially oriented film is shown. As illustrated, the precursor film 10a is directed to an orientation unit of the film 100 or machine direction orienter (MDO), such as that available commercially from Marshall and illams, Co. of Providence. , Rhode Island The MDO has a plurality of stretching rollers (such as 5 to 8) that stretch and progressively thin the film in the machine direction, which is the direction of movement of the film through the process as shown in Fig. 3. While the MDO 100 is illustrated with eight rollers, it should be understood that the number of rollers may be higher or lower, depending on the level of stretching desired and the degrees of stretching between each roller. The movie can Stretch with discrete stretching operations the same simple as multiple. It should be noted that some of the rollers in an MDO device may not work at progressively higher speeds. If desired, some of the rollers of the MDO 100 can act as preheating rollers. If present, these first rollers heat the film 10a above the ambient temperature (eg, to 125 DF). The progressively faster speeds of the adjacent rollers in the MDO act to stretch the film 10a. The speed at which the stretching rollers rotate determines the amount of stretch in the film and the final weight of the film.

The resulting film 10b can then be rolled and stored on a pickup roller 60. Although not shown here, various potential additional processing and / or finishing steps known in the art, such as cutting, processing, forming of openings, printing graphics , or lamination of the film with other layers (e.g., nonwoven fabric weft materials), may be performed without departing from the spirit and scope of the invention.

The film of the present invention may be mono- or multi-layered. Multilayer films can be prepared by co-extruding the layers, extrusion coating, or by any conventional layering process. For example, the movie may contain two (2) to fifteen (15) layers, and in some modalities, from three (3) to twelve (12) layers. Such multilayer films typically contain at least one base layer and at least one skin layer, but may contain any desired number of layers. For example, the multilayer film can be formed from a base layer and one or more skin layers, wherein the base layer is formed from the thermoplastic composition of the present invention. In most embodiments, the skin layer (s) is formed from a thermoplastic composition as described above. It should be understood, however, that other polymers may also be employed in the skin layer (s), such as polyolefin polymers (e.g., linear low density polyethylene (LLDPE) or polypropylene).

The thickness of the film of the present invention may be relatively small to increase flexibility. For example, the film may have a thickness of about 50 microns or less, in some embodiments from about 1 to about 40 microns, in some embodiments from about 2 to about 35 microns, and in some embodiments, from about 5 to about 30 microns . Despite having a small thickness, the film of the present invention is nevertheless capable of retaining good mechanical properties during use. A parameter that is indicative of the relative dry strength of the film is the ultimate tensile strength, which is equal to the maximum stress obtained in a stress-strain curve, as obtained according to the ASTM D638-08 standard. Desirably, the film of the present invention exhibits a maximum stress (when dry) in the machine direction ("MD") of from about 10 to about 100 Megapascals (MPa), in some embodiments from about 15 to about 70 MPa, and in some embodiments, from about 20 to about 60 MPa, and a maximum machine direction ("CD") tension of from about 2 to about 40 Megapascals (MPa), in some embodiments from about 4 to about 40 MPa, and in some embodiments, from about 5 to about 30 MPa.

Although it has a good resistance, the film is relatively ductile. A parameter that is indicative of the ductility of the film is the percentage of deformation of the film at its breaking point, determined by the tension-strain curve, as obtained according to the ASTM D608-08 standard. For example, the percentage of deformation at the break of the film in the machine direction may be about 100% or more, in some embodiments about 150% or more, and in some embodiments, from about 200% to about 600%. Likewise, the percentage of deformation in the breakage of the film in the direction transverse to the machine can be about 200% or more, in some embodiments about 250% or more, and in some embodiments, from about 300% to about 800%. Another parameter that is indicative of ductility is the modulus of elasticity of the film, which is equal to the ratio of the tensile stress to the tensile strain and is determined from the slope of a stress-strain curve. For example, the film typically exhibits a modulus of elasticity (when dry) in the machine direction ("MD") of from about 10 to about 400 Megapascals ("MPa"), in some embodiments from about 20 to about 200 MPa, and in some embodiments, from about 40 to about 80 MPa, and a cross machine direction ("CD") module from about 10 to about 400 Megapascals ("MPa"), in some embodiments from about 20 to about 200 MPa, and in some embodiments, from about 40 to about 80 MPa.

If desired, the film of the present invention can be laminated to one or more nonwoven fabric weft coatings to reduce the coefficient of friction and improve the fabric-like feel of the composite surface. Exemplary polymers for use in the formation of nonwoven fabric weft coatings may include, for example, polyolefins, for example, polyethylene, polypropylene, polybutylene, etcetera; polytetrafluoroethylene; polyesters, for example, polyethylene terephthalate and so on; polyvinyl acetate; polyvinyl acetate chloride; polyvinyl butyral; acrylic resins, for example, polyacrylate, polymethylacrylate, polymethylmethacrylate, and the like; polyamides, for example, nylon; polyvinyl chloride; polyvinylidene chloride; polystyrene; polyvinyl alcohol; polyurethane, · polylactic acid; copolymers of these; etc. If desired, biodegradable polymers can also be employed, such as those described above. Synthetic or natural cellulose polymers can also be used, including but not limited to cellulose esters, cellulose ethers, cellulose nitrates, cellulose acetates, cellulose acetates butyrates, ethyl cellulose; regenerated celluloses, such as viscose, rayon, et cetera. It should be noted that the polymer (s) may also contain other additives, such as process aids or treatment compositions for imparting desired properties to the fibers, residual amounts of solvents, pigments or dyes, and the like.

The monocomponent and / or multicomponent fibers can be used to form the nonwoven fabric weft coating. The monocomponent fibers are generally formed from a polymer or mixture of extruded polymers from a single extruder. The multifunctional fibers are usually formed to from two or more polymers (eg, bicomponent fibers) extruded from separate extruders. The polymers may be disposed substantially in different areas constantly placed across the cross section of the fibers. The components may be arranged in any desired configuration, such as shell-core, side-by-side, pie, island-in-the-sea, three islands, porthole, or other various arrangements known in the art. In addition, multicomponent fibers having various irregular shapes can be formed.

Fibers of any desired length can be used, such as staple fibers, continuous fibers, and the like. In a particular embodiment, for example, staple fibers having a fiber length in the range of about 1 to about 150 millimeters, in some embodiments of about 5 to about 50 millimeters, in some embodiments of about 10 to about 40 millimeters can be used. , and in some modalities, from approximately 10 to approximately 25 millimeters. Although not required, carding techniques can be employed to form fibrous strata with staple fibers as is well known in the art. For example, the fibers can be formed into a carded web by placing bales of the fibers in a selector that separates the fibers. Next, the fibers are sent through a combing or carding unit that further separates and aligns the fibers in the machine direction so as to form a web of fibrous nonwoven fabric oriented in the machine direction. The carded web can then be joined using known techniques to form a woven web of carded non-woven fabric.

If desired, the nonwoven fabric weft coating used to form the nonwoven fabric composite may have a multilayer structure. Suitable multi-layered materials may include, for example, spunbond / meltblown / spunbond (SMS) laminates and spunbond / meltblown (SM) laminates. Another example of a multi-layered structure is a spunbonded web produced on a multiple rotating bank machine in which a rotating bank deposits the fibers on a fiber layer deposited by a previous rotating bank. Such an individual web of non-woven fabric joined by spinning can also be considered as a multi-layered structure. In this situation, the various strata of fibers deposited in the nonwoven fabric web may be the same, or they may be different in basis weight and / or in terms of composition, type, size, level of curl, and / or the shape of the fibers produced. As another example, a single web of non-woven fabric can be provided as two or more individually produced layers of a spunbonded web, a carded web, and the like, which have been bonded together to form the nonwoven fabric weft. These individually produced strata may differ in terms of production method, basis weight, composition, and fibers as discussed above. A nonwoven fabric weft coating may also contain an additional fibrous component so that it is considered a compound. For example, a web of non-woven fabric can be woven with another fibrous component using any of a variety of interlacing techniques known in the art (eg, hydraulics, air, mechanics, etc.). In one embodiment, the non-woven fabric web is integrally intertwined with cellulosic fibers using hydraulic interlacing. A typical hydraulic entanglement process uses water streams in high pressure jets to entangle the fibers to form a highly interwoven consolidated fibrous structure, for example, a nonwoven fabric web. The fibrous component of the compound can contain any desired amount of the resulting substrate.

The basis weight of the nonwoven fabric coating generally can vary, such as from about 5 grams per square meter ("g / m2") to 120 g / m2, in some embodiments from about 8 g / m2 to about 70 g / m2 , and in some embodiments, from about 10 g / m2 to about 35 g / m2. When multiple nonwoven fabric weft liners are used, such materials they may have equal or different base weights.

IV. Applications The film of the present invention can be used in a wide variety of applications, such as a packaging film, such as a single wrapper, a packaging pocket, or a disposal bag of a variety of items, such as food products, products of paper (for example, tissues, wipes, paper towels, etc.), absorbent articles, et cetera. Various pocket, wrap or bag configurations suitable for absorbent articles are described, for example, in U.S. Pat. 6,716,203 from Sorebo, and others and 6,380,445 from Moder, and others, as well as the publication of U.S. Patent Application No. 2003/0116462 of Sorebo, and others, which are incorporated herein in their entirety as a reference for all purposes.

The film can also be used in other applications. For example, the film can be used in an absorbent article. An "absorbent article" generally refers to any article capable of absorbing water or other fluids. Examples of some absorbent articles include, but are not limited to, absorbent personal care articles, such as diapers, training pants, absorbent underwear, incontinence articles, feminine hygiene products (eg, sanitary napkins, pantiprotectores), swimsuits, baby wipes, etc .; medical absorbent articles, such as garments, fenestration materials, protectors, bed pads, bandages, absorbent cloths, and medical towels; wipes for food service, articles of clothing, etcetera. Various examples of such absorbent articles are disclosed in U.S. Pat. 5,649,916 of DiPalma, and others; 6,110,158 to Kielpikowski; 6,663,611 to Blaney, and others, which are hereby incorporated by reference in their entirety for all purposes. Still other suitable articles are described in the publication of the United States patent application no. 2004/0060112 Al of Fell et al., As well as in U.S. Patent Nos. 4,886,512 to Damico et al .; 5,558,659 to Sherrod et al .; 6,888,044 to Fell et al .; and 6,511,465 to Freiburger et al., which are hereby incorporated by reference in their entirety for all purposes. Those skilled in the art are well aware of the materials and processes suitable for the formation of such absorbent articles.

In this respect, a particular embodiment of a sanitary napkin that can employ the film of the present invention will now be described in more detail. For purposes of illustration only, an absorbent article may be a sanitary towel for female hygiene. In that embodiment, the absorbent article includes a main body portion containing an upper canvas, an outer covering or lower canvas, an absorbent core placed between the lower canvas and the upper canvas, and a pair of fins extending from each longitudinal side of the main body portion. The upper canvas defines a surface facing the body of the absorbent article. The absorbent core is positioned inwardly from the outer periphery of the absorbent article and includes a body facing side positioned adjacent to the upper canvas and a garment facing surface positioned adjacent to the lower canvas. In a particular embodiment of the present invention, the bottom sheet is a film formed from the thermoplastic composition of the present invention and is generally liquid impervious and optionally vapor permeable. The film used to form the lower canvas can be laminated to one or more nonwoven fabric weave linings as described above.

The upper canvas is generally designed to be in contact with the user's body and is permeable to liquids. The upper canvas may surround the absorbent core so that it completely encloses the absorbent article. Alternatively, the upper canvas and the lower canvas may extend beyond the absorbent core and join together peripherally, either fully or partially, using known techniques. Typically, the upper canvas and the lower canvas are joined by adhesive bonding, ultrasonic bonding, or any other suitable bonding method known in the art. The upper canvas is sanitary, clean in appearance, and somewhat opaque to hide the bodily discharges collected in and absorbed by the absorbent core. The upper canvas also exhibits good transfer and rewet characteristics that allow the bodily discharges to quickly penetrate through the upper canvas to the absorbent core, but do not allow the body fluid to flow back through the upper canvas to the wearer's skin. For example, some suitable materials that can be used for the upper canvas include non-woven fabric materials, perforated thermoplastic films, or combinations thereof. A non-woven fabric made of polyester, polyethylene, polypropylene, two-component, nylon, rayon, or similar fibers can be used. For example, a uniform white material bonded by spinning is particularly desirable because the color exhibits good masking properties to conceal the menstrual flow passing through it. U.S. Patent No. 4,801,494 from Datta, and others and 4,908,026 from Sukiennik, and others teach various coating materials that can be used in the present invention.

The upper canvas may also contain a plurality of openings (not shown) formed through it to allow that the body fluid passes more easily to the absorbent core. The openings may be arranged randomly or uniformly along the upper canvas, or they may be located only in the narrow longitudinal band or strip disposed along the longitudinal axis of the absorbent article. The openings allow the rapid penetration of body fluid down into the absorbent core. The size, shape, diameter and number of openings can be varied to suit your own particular needs.

The absorbent article also contains an absorbent core placed between the upper canvas and the lower canvas. The absorbent core may be formed from a single absorbent member or a composite containing separate and distinct absorbent members. It must be understood, however, that any number of absorbent members can be used in the present invention. For example, in one embodiment, the absorbent core may contain an input member (not shown) positioned between the upper canvas and a transfer delay member (not shown). The inlet member can be made of a material that is capable of rapidly transferring, in the z-direction, the body fluid that is delivered to the upper canvas. The entry member can generally have any desired shape and / or size. In one embodiment, the entry member has a rectangular shape, with a length equal to or less than the total length of the absorbent article, and a width less than the width of the absorbent article. For example, a length of between about 150 mm to about 300 mm and a width of between about 10 mm to about 60 mm can be used.

Any of a variety of different materials may be used for the entry member to perform the functions mentioned above. The material can be synthetic, cellulose, or a combination of synthetic and cellulose materials. For example, air-laid cellulosic fabrics may be suitable for the entry member. The cellulosic fabric laid to air may have a basis weight in the range of about 10 grams per square meter (g / m2) to about 300 g / m2, and in some embodiments, between about 100 g / m2 to about 250 g / m2 . In one embodiment, the cellulosic fabric laid to the air has a basis weight of approximately 200 g / m2. The fabric stretched to the air can be formed from hard wood and / or softwood fibers. The fabric stretched to the air has a fine pore structure and provides an excellent capacity of absorption by capillarity, especially for the menstrual fluid.

If desired, a transfer delay member (not shown) can be placed vertically below the entry member. The transfer delay member may contain a material that is less hydrophilic than the other absorbent members, and can generally be characterized as substantially hydrophobic. For example, the transfer delay member may be a fibrous web of nonwoven fabric composed of a relatively hydrophobic material, such as polypropylene, polyethylene, polyester or the like, and furthermore may be composed of a mixture of such materials. An example of a material suitable for the transfer delay member is a spunbond fabric composed of polypropylene, multilobular fibers. More examples of suitable transfer delay member materials include spunbond webs composed of polypropylene fibers, which may be round, trilobal or polylobular in cross-sectional shape and which may be hollow or solid-structured. Typically the frames are joined, such as by thermal bonding, to above about 3% about 30% of the area of the weft. Other examples of suitable materials that can be used for the transfer delay member are described in U.S. Pat. 4,798,603 from Meyer, and others and 5,248,309 from Serbiak, and others. To adjust the performance of the invention, the transfer delay member can be further treated with a selected amount of surfactant to increase its initial wettability.

The transfer delay member can generally have any size, such as a length of about 150 mm to about 300 mm. Typically, the length of the transfer delay member is approximately equal to the length of the absorbent article. The transfer delay member may also be as wide as the entry member, but typically it is wider. For example, the width of the transfer delay member may be between about 50 mm to about 75 mm, and particularly about 48 mm. Typically the transfer delay member has a lower basis weight than that of the other absorbent members. For example, the basis weight of the transfer delay member is typically less than about 150 grams per square meter (g / m2), and in some embodiments, between about 10 g / m2 to about 100 g / m2. In a specific embodiment, the transfer delay member is formed from a spunbonded web having a basis weight of about 30 g / m2.

In addition to the aforementioned members, the absorbent core may also include an absorbent member member (not shown), such as a coform material. In this case, the fluids can be absorbed from the transfer delay member towards the absorbent member. The absorbent composite member may be formed separately from the input member and / or the transfer delay member, or may be formed simultaneously therewith. In one embodiment, for example, the compound member Absorbent may be formed on the transfer delay member or the inlet member, which acts as a carrier during the coform process described above.

While various configurations of an absorbent article have been described above, it should be understood that other configurations are also included within the scope of the present invention. Furthermore, the present invention is not limited in any way to the lower canvases and the film of the present invention can be incorporated into a variety of different components of an absorbent article. For example, a release liner of an absorbent article may include the film of the present invention.

The present invention will be better understood with reference to the following examples.

Test methods Traction properties The tensile properties (maximum stress, modulus, deformation at break, and energy per volume at break) of the films were tested on a Sintech 1 / D traction frame. The test was performed in accordance with ASTM D638-08. The film samples were cut into dog bone with a central width of 3.0 mm before the test. The dog bone film samples were held in place using tweezers in the Sintech device with a caliber length of 18.0 mm. Film samples stretched at a speed of crosspiece of 12.7 cm (5.0 inches / min) until the break occurred. Five samples were tested for each film in the machine direction (MD) and in the transverse direction (CD). A computer program called TestWorks 4 was used to collect the data during the test and to generate a curve of the tension as a function of the deformation from which a series of properties was determined, including the module, the maximum voltage, the lengthening, and the energy to break. flow index The melt index was determined in accordance with ASTM D-1238 at a temperature of 190 ° C, a load of 2.16 kg, and a release time of 6 minutes. A Model MP600 fusion indexer from Tinius Olsen Testing Machine Company, Inc. was used to measure the flow rates.

Moisture analysis The moisture content was determined using a "loss on drying" method using a Compurac® moisture analyzer manufactured by Arizona Instrument. More particularly, the initial weight of the sample was measured. This sample was then placed in an oven at 130 ° C to remove the water, cooled to room temperature, and reweighed. The moisture content can be determined as parts per million ("ppm") or weight percent (% by weight) as follows.

Moisture content (ppm) = [(Initial mass - Mass final) / Initial mass] * 1,000,000 Moisture content (% by weight) = [(Initial mass - Final mass) / Initial mass] * 100 Materials employed The following materials were used in the examples: Cargill corn starch gel was purchased from Cargill (Cedar Rapids, IA), Glycerin (Emery ™ 916) was purchased from Cognis Corporation (Cincinnati, OH); ECOFLEX ™ F BX 7011, an aromatic aliphatic copolyester, was purchased from BASF (Ludwigshafen, Germany); DOWLEX ™ EG 2244G polyethylene resin was purchased from Dow Chemical Company (Midland, MI) and FUSABOND® MB 528D, a chemically modified polyethylene resin, was purchased from DuPont Company (Wilmington, Delaware).

Equipment used Extruder ZSK-30 The ZSK-30 extruder (Werner and Pfleiderer Corporation, Ramsey, NJ) is a co-rotating twin-screw extruder with a diameter of 30 mm and a screw length of up to 1328 mm. The extruder has 14 cylinders. The first cylinder received the mixture of starch, Ecoflex copolyesters, polyolefins, compatibilizers, additives, and so on. When the glycerin injection was used, it was injected into cylinder 2 with a pressure injector connected with an Eldex pump (Napa, CA). He vent opened at the end of the extruder to release moisture.

HAAKE Rheomex 252 The Haake Rheomex 252 (Haake, Karlsruhe, Germany) is a single screw extruder with a diameter of 18.75 mm and a screw length of 450 mm.

HAAKE Rheocord 90 The Haake Rheocord 90 (Haake, Karlsruhe, Germany) is a computer-controlled torque rheometer. It is used to control the rotor speed and temperature settings in the HAAKE Rheomex 252.

EXAMPLES 1-5 The ability to form a thermoplastic composition using the process of the present invention was demonstrated. More particularly, the composition was formed of 25% by weight of thermoplastic starch (corn starch and glycerin), 34% by weight of DOWLEX ™ EG 2244G polyethylene, 3% by weight of FUSABOND ™ MB 528D, and 38% by weight of ECOFLEX ™ F BX 7011. Maize starch was fed using a ZSK-30 double-screw dust feeder at a rate of 3.4 kg (7.5 lb / hr). The glycerin was used to fill buckets of 18.92 1 (5 gallons) and heated before mixing the resin. The glycerin was pumped directly into the melt stream of the extruder using a three-head liquid pump at approximately 18.9 g / min, equivalent to 1.13 kg (2.5 lb / hr). He Polyethylene ("PE") DOWLEX ™ was measured in a 18.92 1 (5 gallon) cuvette and mixed by hand with FUSABO D ™ 528 ("FB"). The mixture was fed into the throat of the extruder at a rate of 6.65 kg (14.68 lb / hr) through a single screw granule feeder. The ECOFLEX ™ copolyester was fed into the throat using a single screw feeder at a rate of 6.8 ka (15 lb / hr).

The processing conditions are set forth below in Table 1.

Table 1: Process conditions The resulting strands of the mixture were cooled in air on a band by a series of fans located above the band. The cold strands were collected on a cardboard sheet and then crushed into granules for further processing. The films were cast using a Haake Rheomex 252 connected to a Haake Rheocord 90, which was responsible for controlling and adjusting torque, screw speed, and heating. The granules obtained from ZSK-30 extruder was fed by flooding in the Haake extruder for casting the film. A 20.32 cm (8 inch) film die was used in conjunction with a cooled roll and pick system to obtain a film having a thickness of approximately 25.4 micrometers.

The resulting films were stored in a standard condition conditioning room overnight and the tensile properties were tested as indicated above. The MD and CD properties for the films are discussed below in Tables 2-3. It should be noted that the films of Examples 1 and 5 showed a significant number of large holes. These holes were avoided when physical properties were tested.

Table 2: Traction properties in MD Table 3: Traction properties on CD EXAMPLES 6-8 The ability to form a thermoplastic composition using the process of the present invention was demonstrated. More particularly, the composition was formed of 25% by weight of thermoplastic starch (corn starch and glycerin), 34% by weight of DOWLEX ™ EG 2244G polyethylene, 3% by weight of FUSABOND ™ MB 528D, and 38% by weight of ECOFLEX ™ F BX 7011. Maize starch was fed using a ZSK-30 double-screw dust feeder at a rate of 3.4 kg (7.5 lb / hr). The glycerin was used to fill buckets of 18.92 1 (5 gallons) and heated before mixing the resin. The glycerin was pumped directly into the melt stream of the extruder using a three-head liquid pump at approximately 18.9 g / min, which equals 1.13 kg (2.5 lb / hr). He polyethylene ("PE") DOWLEX ™ was measured in a 5-gallon bucket and mixed by hand with FUSABOND ™ 528 ("FB"). The mixture was fed into the throat of the extruder at a rate of 6.65 kg (14.68 lb / hr) through a single screw granule feeder. The ECOFLEX ™ copolyester was fed into the throat using a single screw feeder at a rate of 6.81kg (15 lb / hr).

The resulting strands were cooled in a water bath with variable water exposure lengths of 1.52m, 3.04m or 4.57m (5 feet, 10 feet or 15 feet). The cold strands were collected on a cardboard sheet and then crushed into granules for further processing. The processing conditions for the samples are set forth below in Table 4.

Table 4: Conditions of the proc After immersing in the 5-foot water immersion, the strands of Example 6 were too ductile to granulate because they did not completely cool. In Examples 7 and 8, cooling was sufficient to allow the strands to cool and continuous granulation was possible. The films were filtered using a Haake Rheomex 252 connected to a Haake Rheocord 90, which was responsible for controlling and adjusting torque, screw speed, and heating. The granules obtained from the extruder ZSK-30 were fed by flooding in the Haake extruder for casting the film. An 8-inch film die was used together with a cooled roll and pick system to obtain a film having a thickness of approximately 25.4 microns. The conditions of the laundry are summarized in Table 5 below.

Table 5: Conditions of the laundry The resulting films were stored in a standard condition conditioning room overnight and the tensile properties were tested as indicated above. The MD and CD properties for the films are discussed below in Tables 6-7.

Table 6: Traction properties in MD Table 7: Traction properties on CD As indicated, the maximum DC voltage, ductility, and energy at break of the water-cooled films of Examples 6-8 were high.

EXAMPLE 9 The ability to form a thermoplastic composition using the process of the present invention was demonstrated. More particularly, the composition was formed of 19% by weight of corn starch, 6% by weight of glycerin, 34% by weight of DOWLEX ™ EG 2244G polyethylene, 3% by weight of FUSABOND ™ MB 528D, and 38% by weight of ECOFLEX ™ F BX 7011. DOWLEX ™ EG 2244G polyethylene, FUSABOND ™ MB 528D, and ECOFLEX ™ F BX 7011 initially they were mixed dry and then fed to a 64 mm co-rotating twin screw extruder (ratio L / D = 38) at a rate of 375 pounds per hour. The extruder had a feed cylinder (Zone 1), six closed cylinders (Zones 2-7), and finally a cylinder with a vacuum stack (Zone 8). The polymer mixture was supplied to the feed cylinder through a double screw gravimetric feeder (Arbo flat tray feeder). The corn starch was further fed to the feed cylinder through a gravimetric feeder (Accurate feeder) at a rate of 95 pounds per hour. Glycerin was pumped directly into the extruder feed cylinder using a gear pump for liquids at approximately 30 lb / hr. A 12-strand die with a diameter of 0.125 inches was used to form strands from the composition. The resulting strands were cooled as shown in Fig. 2. More particularly, the strands were immersed in a water bath with an exposure length of approximately 2.13m (7 feet) in which the water circulates to maintain a cold temperature of the water. Multiple passes of strands and an air knife were used to ensure proper cooling and remove moisture on the surface of the strands before granulation. The cooled strands were granulated and collected in a drum.

The films were cast using a Haake Rheomex 252 connected to a Haake Rheocord 90, which was responsible for controlling and adjusting torque, screw speed, and heating. The granules obtained from the extruder ZSK-30 were fed by flooding in the Haake extruder for casting the film. A 20.32 cm (8 inch) film die was used in conjunction with a cooled roll and pick system to obtain a film having a thickness of approximately 25.4 micrometers. The conditions of the laundry are summarized in Table 8 below.

Table 8: Conditions of the laundry As indicated, the extrusion and die temperatures remained fairly stable, except that Zone 4 fluctuated at a temperature of 283 ° F to 360 ° F. The resin produced in this example was further evaluated for the moisture content and the melt index in the manner described above. The moisture content was 8860 ppm and the flow index was 2.13 grams per 10 minutes (190 ° C, 2.16 kg load).

EXAMPLE 10 The films were formed as described in Example 9, except that the cast conditions summarized in Table 9 below were used.

Table 9: Conditions of the laundry As indicated, the extrusion temperatures were higher than those of Example 9. The temperature of the die body was high in the early stages due to a higher screw speed, 330 rpm. After reducing the screw speed to 250 rpm, the temperature of the die body was slowly cooled to the point of fixed deformation. The resin produced in this example was further evaluated for moisture content and flow rate at run times of 60 minutes, 90 minutes, and 120 minutes. The moisture content was 4000 ppm at 60 minutes, 2600 ppm at 90 minutes, and 4378 at 120 minutes. The flow rate was 0.28 g / 10 min at 60 minutes, 0.18 g / 10 min at 90 minutes, and 0.31 g / 10 min at 120 minutes.

EXAMPLE 11 The films were cast from the samples of Examples 9 and 10 using a Haake Rheomex 252 connected to a Haake Rheocord 90, which was responsible for controlling and adjusting torque, screw speed, and heating. The granules obtained from the extruder ZSK-30 were fed by flooding in the Haake extruder for casting the film. An 8-inch film die was used in conjunction with a cooled roll and pick system to obtain a film having a thickness of approximately 25.4 microns. The conditions of the laundry they are summarized in Table 10 below.

Table 10: Conditions of the laundry The resulting films were stored in a standard condition conditioning room overnight and the tensile properties were tested as indicated above. The average MD and CD properties of the films are discussed below in Tables 11-12.

Table 11: Traction properties in MD Table 12: Traction properties As indicated, the elongation and maximum tension values MD / CD of Example 9 are quite high. Example 10 showed values of maximum stress and elongation values lower than expected, which are believed to be due to holes formed in the film during casting due to unintentional degradation of the starch during mixing.

While the invention has been described in detail with respect to the specific embodiments thereof, it will be appreciated that those skilled in the art, upon reaching an understanding of the foregoing, can readily conceive alterations, variations, and equivalents to these embodiments. Accordingly, the scope of the present invention should be evaluated as that of the appended claims and any equivalent thereto.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims

CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A method for forming a thermoplastic composition, characterized in that it comprises: supplying a renewable biopolymer, a polyolefin, and a compatibilizer to a feed section of an extruder, wherein the compatibilizer has a polar component and a non-polar component; directly injecting a liquid plasticizer into the extruder so that the plasticizer is mixed with the biopolymer, the polyolefin, and the compatibilizer to form a mixture; Y melt processing the mixture into the extruder to form the thermoplastic composition. 2. The method according to claim 1, characterized in that the biopolymer is a starch polymer. 3. The method according to claim 2, characterized in that the starch polymer is a corn starch. 4. The method of compliance of any of the preceding claims, characterized in that the plasticizer is a sugar alcohol. 5. The method according to claim 4, characterized in that the plasticizer is glycerin. 6. The method of compliance of any of the preceding claims, characterized in that the relationship 5 by weight of the renewable biopolymers to the plasticizers in the thermoplastic composition is from about 1 to about 10. 7. The method of compliance of any of the preceding claims, characterized in that the plasticizers constitute from about 0.5% by weight to about 20% by weight of the composition. 8. The method of compliance of any of the preceding claims, characterized in that the polyolefins constitute from about 10% by weight to about 50% by weight of the polymer content of the thermoplastic composition. 9. The method of compliance of any of the preceding claims, characterized in that the polyolefin is a copolymer of an ethylene and an α-olefin. 0 io. The method of compliance of any of the preceding claims, characterized in that the compatibilizers constitute from about 0.1% by weight to about 15% by weight of the composition. 11. The method of conformity of any of the preceding claims, characterized in that the component Non-polar is provided by an olefin. 12. The method according to claim 11, characterized in that the compatibilizer includes one or more functional groups grafted onto a polyolefin backbone. 13. The method according to claim 12, characterized in that the polyolefin backbone is grafted with maleic anhydride. 14. The method of compliance of any of the preceding claims, characterized in that it comprises supplying a biodegradable polyester to the feed section of the extruder so that the plasticizer is also mixed with the biodegradable polyester. 15. The method according to claim 14, characterized in that the biodegradable polyesters constitute from about 10% by weight to about 70% by weight of the polymer content of the thermoplastic composition and the renewable biopolymers constitute from about 1% by weight to about 35% by weight of the polymer content of the thermoplastic composition. 16. The method according to claim 14, characterized in that the biodegradable polyester is an aliphatic-aromatic copolyester. 17. The method of compliance of any of the preceding claims, characterized in that the Plasticizer is supplied to a feed section of the extruder. 18. The method of compliance of any of the preceding claims, characterized in that the plasticizer is supplied to a melting section of the extruder which is located downstream of the feed section. 19. The method of compliance of any of the preceding claims, characterized in that the mixture is melt processed at a temperature of about 100 ° C to about 300 ° C. 20. A method for forming a film, characterized in that it comprises: supplying a renewable biopolymer, a polyolefin, and a compatibilizer to a feed section of an extruder, wherein the compatibilizer has a polar component and a non-polar component; directly injecting a liquid plasticizer into the extruder so that the plasticizer is mixed with the biopolymer, the polyolefin, and the compatibilizer to form a mixture; melt processing the mixture within the extruder to form a thermoplastic composition; Y Extrude the thermoplastic composition through a die and onto a surface to form the film, in where the film has a thickness of approximately micrometers or less.